Fluid-operated braking systems such as air brake systems have long been used to control the movement of motor vehicles in a safe and effective manner. In particular, air brakes are commonly used on commercial vehicles, such as trucks which typically have large gross vehicle weights. The considerable inertial mass of these heavy-duty vehicles in combination with the high speeds at which they travel require a braking system which responds rapidly with substantial braking power. One system component which is instrumental in the operation of air brake systems is the brake actuator. The brake actuator provides the force necessary when braking a vehicle. Commercial air brake actuators can actuate the normal surface brakes as well as parking/emergency brakes. The brake actuators, also known as spring brakes, typically have a network of air chambers defined by one or more diaphragms and/or pistons and a plurality of springs which operate to provide the appropriate braking action in response to inputs by the vehicle driver. In the event an air braking system loses pressure, the brake actuator automatically engages the vehicle brakes.
In brake actuators of this type, the diaphragms are typically flexible, cup-shaped and have an outer radial rim which is received and compressed between flange portions of a housing and cover. Such diaphragms are generally formed of a rubber material with a fibrous reinforcement disposed therein. Diaphragms are often molded in an ovoid shape making it somewhat difficult to align and assemble the diaphragm in the brake actuator housing. The difficulties in assembly can often lead to leakage of the seal established between the diaphragm and the flange portions of the housing and cover. Great care is taken in the manufacture of the brake actuators in order to test for leaking actuator assemblies, identify leaking brake actuators assemblies, and to eliminate leaking brake actuator assemblies. If the brake actuator assembly leaks, the brake actuator may fail.
In this type of brake actuator assembly, it is important during assembly that the rim portion of the flexible diaphragm be properly seated and aligned prior to being compressed between the opposed radial flanges of the housing and the cover. During assembly the flexible diaphragm must be coaxially aligned with the radial flanges of the opposed housing members. However, due to the ovoid shape of typical diaphragms as received from the manufacturer and curvature of the surfaces of the opposed radial flanges, alignment of the diaphragm and housing is difficult, thereby increasing the potential for leakage.
Additionally, the thickness of radial rim portion of the diaphragm causes difficulty in the assembly of the brake actuator. The thickness of the rim portion of the diaphragm requires that the housing and cover be placed in compression against the diaphragm during assembly in order to facilitate the application of a band clamp which holds the housing and cover in sealing engagement with the diaphragm.
Accordingly, it would be both advantageous and desirable to have a diaphragm which can more easily be positioned and seated during assembly of the brake actuator to reduce the amount of leaking brake actuator assemblies and which also aids in the assembly process by eliminating the step of compressing together the housing and the cover in order to attach and fasten the band clamp.